“Where your treasure is, there your heart will be also,” reads a placard near where the heart of composer Frédéric Chopin lies. It is sealed in a glass jar and concealed by a stone pillar.

In Poland, where the organ has rested off and on for a century and a half, the site is a piece of a nation’s soul; Chopin’s music may belong to the ages, but Poland has claimed the half-Polish composer and pianist as its own.

Despite the mystery and intense scientific and academic curiosity surrounding his early death in 1849 at the age of 39, the country has resisted calls to exhume the heart and subject it to DNA inspection.

It has only been removed from the resting place, where it was brought under the cover of secrecy shortly after Chopin’s death, on fewer than a handful of occasions.

Historians and scientists have clamored for years to collect evidence that would say definitively whether Chopin died of tuberculosis or perhaps cystic fibrosis, which had not yet been discovered at the time of his death.

Most recently, a delicate operation to get a rare glimpse of the organ was undertaken in total secrecy and in the dead of the night by of team of scientists, officials, the Polish culture minister and the archbishop of Warsaw in April.

No one knew that the heart had been removed until months later, in September, when the first details of their inspection became public. And on Monday, a captivating Associated Press report revealed the reasons behind the covert operation:

With a feeling of mystery hanging in the air, they worked in total concentration, mostly whispering, as they removed the heart from its resting place and carried out the inspection — taking more than 1,000 photos and adding hot wax to the jar’s seal to prevent evaporation. Warsaw’s archbishop recited prayers over the heart and it was returned to its rightful place. By morning, visitors to the church saw no trace of the exhumation.

One forensic scientist on the team, Tadeusz Dobosz, described the moment as more spiritual than scientific.

“The spirit of this night,” Dobosz told the AP, “was very sublime.”

It’s easy to understand why. The composer’s preserved heart lies inside Warsaw’s Holy Cross Church, where it is something of a shrine to Polish culture and political independence.

“The fact that Warsaw was so totally destroyed in World War II means that anything old is precious,” said Monika Strugala, who in 2010 was tasked with coordinating Poland’s bicentennial celebration of Chopin, according to the New York Times. “Even if only a few pieces of the organ survived and are original, we still say it is the one that Chopin played.”

The heart landed in Nazi hands during World War II. They returned it to priests at Holy Cross as a goodwill gesture (but only after the Nazis had violently crushed a Warsaw uprising in 1944). The priests hid it until the end of the war.

Shortly after the war, the organ was examined and was found to be perfectly preserved, all the more reason to be jittery about disturbing the fragile historical peace.

“Records show it is in perfect condition, so to tamper with it risks destroying it,” Grzegorz Michalski, director of Poland’s National Fryderyk Chopin Institute, told Agence France-Presse in 2008.

Michalski said at the time that Chopin’s two living descendants were evenly split for and against DNA testing. Ultimately, it was never done.

As for Chopin’s body, that lies in Paris, where he died during a self-imposed exile from his homeland. The son of a Polish mother and French father, Chopin is believed to have had one dying wish: That his body be opened up and his heart returned to Poland.

His wish was granted.

Chopin’s sister, Ludwika, had his heart removed, preserved in alcohol — cognac, the strongest available at the time — and hermetically sealed in a crystal jar. The jar was placed in an urn made of mahogany and oak. Ludwika whisked it away — perhaps under her skirt, as the story goes — to Warsaw.

More than 160 years later, despite the absence of any definitive testing, the latest inspection of Chopin’s heart did reveal some clues about his cause of death.

In September, when word of the operation first emerged, the AP reported that scientists believed the heart showed signs of lung disease and tuberculosis. And the color of the liquid in which it is still preserved indicates that the alcohol used in 1849 was likely cognac.

Unlike one lucky AP reporter who was given a glimpse of the photos taken of the heart, few people will ever see it in the flesh.

There are, however, plans to unearth it again — in 50 years.